The present invention relates to a seat which includes a plurality of portions which can be varied with respect to form and hardness.
Various kinds of seats for a motor vehicle of this type have been proposed in past years. One such seat is disclosed, in JP 61-257333. This seat has a side support portion, a center support portion , and a front support portion which include support members therein. The contour of the seat is variable by expanding and contracting each of the support members. In the event of long driving, each of the support members is controlled at a predetermined cycle by a timer so as to vary the contour of the seat. This variation in contour of the seat results in a periodic change in the posture of a seat occupant, decreasing the fatigue of the seat occupant during driving.
With such a known seat for a motor vehicle, however, since each of the support members is controlled only in a periodic manner, i.e., to vary with a predetermined period of time set by the timer, the contour of the seat may be varied even when the seat occupant is not fatigued, causing the seat occupant discomfort.
Referring to FIG. 6, it can be seen that there is a correlation between the frequency of posture changing motion, i.e., the frequency of physical movement of the seat occupant and the fatigue level of the occupant. It is also understood from FIG. 6 that the higher the frequency of the posture changing motion, the higher the fatigue level.
Further, it is revealed that a body of the seat occupant shows different vital reactions in accordance with the fatigue level of the seat occupant.